Loudspeaker drivers are a type of audio transducer that generate sound by oscillating a diaphragm using an actuating mechanism that may be electromagnetic, electrostatic, piezoelectric or any other suitable moveable assembly known in the art. The driver is generally contained within a housing. In conventional drivers, the diaphragm is a flexible membrane component coupled to a rigid housing. Loudspeaker drivers therefore form resonant systems where the diaphragm is susceptible to unwanted mechanical resonance (also known as diaphragm breakup) at certain frequencies during operation. This affects the driver performance.
An example of a conventional loudspeaker driver is shown in FIGS. 55A-55B. The driver comprises a diaphragm assembly mounted by a diaphragm suspension system to a transducer base structure. The transducer base structure comprises a basket J113, magnet J116, top pole piece J118, and T-yoke J117. The diaphragm assembly comprises a thin-membrane diaphragm, a coil former J114 and a coil winding J115. The diaphragm comprises of cone J101 and cap J120. The diaphragm suspension system comprises of a flexible rubber surround J105 and a spider J119. The transducing mechanism comprises a force generation component being the coil winding held within a magnetic circuit. The transducing mechanism also comprises the magnet J116, top pole piece J118, and T-yoke J117 that directs the magnetic circuit through the coil. When an electrical audio signal is applied to the coil, a force is generated in the coil, and a reaction force, is applied to the base structure.
The driver is mounted to a housing J102 via a mounting system consisting of multiple washers J111 and bushes J107 made of flexible natural rubber. Multiple steel bolts J106, nuts J109 and washers J108 are used to fasten the driver. There is a separation J112 between the basket J113 and the housing J102 and the configuration is such that the mounting system is the only connection between the housing J102 and the driver. In this example, the diaphragm moves in a substantially linear manner, back and forth in the direction of the axis of the cone shaped diaphragm, and without significant rotational component.
As mentioned, the flexible diaphragm coupled to the rigid housing J102, via the suspension and mounting system, forms a resonant system, where the diaphragm is susceptible to unwanted resonances over the driver's frequency range of operation. Also, other parts of the driver including the diaphragm suspension and mounting systems and even the housing can suffer from mechanical resonances which can detrimentally affect the sound quality of the driver. Prior art driver systems have thus attempted to minimize the effects of mechanical resonance by employing one or more damping techniques within the driver system. Such techniques comprise for example impedance matching of the diaphragm to a rubber diaphragm surround and/or modifying diaphragm design, including diaphragm shape, material and/or construction.
Many microphones have the same basic construction as loudspeakers. They operate in reverse transducing sound waves into an electrical signal. To do this, microphones use sound pressure in the air to move a diaphragm, and convert that motion into an electrical audio signal. Microphones therefore have similar constructions to loudspeaker drivers and suffer some equivalent design issues including mechanical resonances of the diaphragm, diaphragm surround and other parts of the transducer and even the housing within which the transducer is mounted. These resonances can detrimentally affect the transducing quality.
Passive radiators also have the same basic construction as loudspeakers, except they do not have a transducing mechanism. They therefore suffer from some equivalent design issues creating mechanical resonances which can all detrimentally affect operation.
It is an object of the present invention to provide improvements in or relating to audio transducers which work in some way towards addressing some of the resonance issues mentioned above or to at least provide the public with a useful choice.